Data is typically recorded into a holographic medium by employing a spatial light modulator (SLM) which produces a data beam from a carrier beam. The data beam is two-dimensional in nature and comprises a rectangular image of a large number of bits arranged in a sequential raster pattern. The data beam and a reference beam (typically originally split from the carrier beam) are separately directed to the holographic medium and intersect and interfere to form an interference wave front that is recorded as a holographic image known as a hologram into the holographic medium. The data is read by providing a reference beam directed to the holographic medium at the location of the hologram and the output beam is directed to an optical sensor. The optical sensor is arranged to detect an image resulting from the interaction of the hologram and the reference beam.
The arrangement of the sequential raster pattern comprises strings of serial data and may be subject to errors that exceed the capabilities of an error correction code applied to the data.